Ambient vs Fermentation temps with a chest freezer

[Fisher kel Tath]

Bumping this up cause I've seemingly found myself in an argument with someone on another forum, saying that taping the temp probe to the fermentor and insulating is only going to guarantee frozen liquid.

[Bugeater]

Bumping this up cause I've seemingly found myself in an argument with someone on another forum, saying that taping the temp probe to the fermentor and insulating is only going to guarantee frozen liquid.

That's a bunch of BS. The last 40-50 batches of mine should have all been frozen is that were true. Taping the probe to the fermenter and insulating tells the controller the exact (or close enough) temperature of the wort. When the temperature drops to the set point of the controller, the controller shuts off the freezer. No way will the temperature continue to drop to freezing unless there is an equipment malfunction or you did something stupid.

While the freezer is actually running trying to get the temperature of the wort down to the set temperature, the ambient temperature inside the freezer can be quite a bit lower than the set temperature. We don't care about that, only the temperature of the wort. Some of the other forums have folks giving advice who have been getting their heads and rectal thermometers mixed up.

Wayne

[Fisher kel Tath]

Bumping this up cause I've seemingly found myself in an argument with someone on another forum, saying that taping the temp probe to the fermentor and insulating is only going to guarantee frozen liquid.

That's a bunch of BS. The last 40-50 batches of mine should have all been frozen is that were true. Taping the probe to the fermenter and insulating tells the controller the exact (or close enough) temperature of the wort. When the temperature drops to the set point of the controller, the controller shuts off the freezer. No way will the temperature continue to drop to freezing unless there is an equipment malfunction or you did something stupid.

While the freezer is actually running trying to get the temperature of the wort down to the set temperature, the ambient temperature inside the freezer can be quite a bit lower than the set temperature. We don't care about that, only the temperature of the wort. Some of the other forums have folks giving advice who have been getting their heads and rectal thermometers mixed up.

Wayne

Yea, that was also my argument, the person even dismissed JZ and Palmer's opinion on the subject as them just being some no name "brew dudes"

[snowcapt]

I was listening to one of the many podcasts about the fluctuation of the temp in the freezers with temp controllers. Jamil stated that the amount of temp fluc. isnt really an issue. As far as the info on here is concerned, I think I will go with what Wayne says. It is a good way to do it. I have yet to do it and I just use ambient temps for my ferments. I live in MN and I have a 3 level house, so I can get on target with just about any temp I need. I start out in the basement and they get to graduate to the next floor accordingly.
And, again, I am super jealous of your newly commandeered system, phooti! Fuckin thing is shiny and beautiful! Oh, the things that will come out of that......
Cheers, man, you are definitely on the right track.
Also, I was thinking the other night about that mash paddle mounted on some sort of motor to ward of the zombies. Cool site and a good read as well. I look forward to new installments. Keep the passion up, brotha!

[cdburg]

I'm definitely not trying to stir up shit here, but I did want to post an example of what I was talking above with my experience with a glass carboy in a freezer for fermentation.

The picture below (not great, but hopefully visible) shows the difference in temperature between a probe taped to the outside of the glass carboy (insulated with silver, reflective bubble wrap) and a probe in a thermowell in the middle of the fermenting beer.



In this case, I was fermenting a Kolsch at 60F. The "Cool" Ranco controller is the probe in the thermowell (running the freezer). The "Heat" Ranco controller is the probe that was attached to the outside of the carboy (for comparison).

In this case, the freezer was running, to knock the temperature back down to 60F from 61F. In the process of cooling the beer, the first thing to cool is the glass carboy, like a bottle of beer in the fridge. In this picture, there is a 5 degree difference between the two probes.

When the freezer isn't running, the two temperatures are usually very close or the same. When the freezer kicks on though, the "outside" probe reaches the desired temp (60F in this case) about 20 minutes before he internal probe. If I used that to control the ferment, it wouldn't be quite as accurate. The liquid wouldn't be cooled to the desired temp, and could get quite warm over time. I actually had problems with fusels in the past before I moved to the thermowell.

As always, your experience my vary, but I've found the thermowell to be more accurate and to produce better beers, in my set up. If you use a refridgerator to control temps (as Jamil does), I don't think it would be as much of an issue since the liquid would be cooled slower. If you ferment in buckets or plastic carboys, I also don't think it would be an issue, since plastic is a better insulator. For glass carboys fermenting in freezers though, I would encourage everyone to test for themselves. You might see something similar to what I have experienced.

[andy77]

I'm definitely not trying to stir up shit here, but I did want to post an example of what I was talking above with my experience with a glass carboy in a freezer for fermentation.

The picture below (not great, but hopefully visible) shows the difference in temperature between a probe taped to the outside of the glass carboy (insulated with silver, reflective bubble wrap) and a probe in a thermowell in the middle of the fermenting beer.



In this case, I was fermenting a Kolsch at 60F. The "Cool" Ranco controller is the probe in the thermowell (running the freezer). The "Heat" Ranco controller is the probe that was attached to the outside of the carboy (for comparison).

In this case, the freezer was running, to knock the temperature back down to 60F from 61F. In the process of cooling the beer, the first thing to cool is the glass carboy, like a bottle of beer in the fridge. In this picture, there is a 5 degree difference between the two probes.

When the freezer isn't running, the two temperatures are usually very close or the same. When the freezer kicks on though, the "outside" probe reaches the desired temp (60F in this case) about 20 minutes before he internal probe. If I used that to control the ferment, it wouldn't be quite as accurate. The liquid wouldn't be cooled to the desired temp, and could get quite warm over time. I actually had problems with fusels in the past before I moved to the thermowell.

As always, your experience my vary, but I've found the thermowell to be more accurate and to produce better beers, in my set up. If you use a refridgerator to control temps (as Jamil does), I don't think it would be as much of an issue since the liquid would be cooled slower. If you ferment in buckets or plastic carboys, I also don't think it would be an issue, since plastic is a better insulator. For glass carboys fermenting in freezers though, I would encourage everyone to test for themselves. You might see something similar to what I have experienced.

You're not stirring things up, good data point.

This would be my question: if you're controlling the temp via a probe taped to the side, what's the actual temp swing of the wort. If the measured temp swings from (in you example) from 61, back down to 60 very quickly because you're measuring the glass temp, then everything equalizes, then the fridge turns back on again and cools back down again very quickly, the wose case scenario is overcycling the fridge. But if the actual wort temp, over the long term stays at 60-61 then that's a good ferment.

Remember that the goal isn't to measure the fermentation temps exactly, but to maintain a desired temp through a whole fermentation.

At any rate, I tape to the side of the carboy, and have great fermentations.

[cdburg]

You're not stirring things up, good data point.

This would be my question: if you're controlling the temp via a probe taped to the side, what's the actual temp swing of the wort. If the measured temp swings from (in you example) from 61, back down to 60 very quickly because you're measuring the glass temp, then everything equalizes, then the fridge turns back on again and cools back down again very quickly, the wose case scenario is overcycling the fridge. But if the actual wort temp, over the long term stays at 60-61 then that's a good ferment.

Remember that the goal isn't to measure the fermentation temps exactly, but to maintain a desired temp through a whole fermentation.

At any rate, I tape to the side of the carboy, and have great fermentations.

From what I can tell, the beer temp isn't reducing for the externally mounted probe. The "outside" probe hits a 1 degree drop in temperature pretty quickly, probably in about 15 minutes. To drop the thermowell probe temperature 1 degree, it takes more like 45 minutes to an hour. In 15 minutes (the time the freezer would run with the external probe location), I don't think the temperature of the beer is dropping too much. I also don't think the glass gets cold enough to drop the beer any further, so I don't think that everything is equalizing at the correct temperature. I actually think that the internal temperature is increasing, since it's not being cooled enough to maintain the correct temp.

To me, it seems like the outside probe is measuring the temperature of the glass, not the beer. When the freezer is not running, it's generally fine, since the glass is roughly the same temp as the beer. When it's being cooled though, measuring the temp of the glass and not the beer seems like it could be inaccurate. Over time, I believe it builds upon itself. I think that is compounded with an especially aggressive yeast (e.g. belgian strains).

To be fair, I am in California, and it gets warm in the room where the freezer is located. The freezer is fighting external temps also, so if it isn't running long enough to cool the fermenting beer, the fermentation can get out of control pretty quickly. I think that's exactly what was happening to me. I was getting fusels. I could taste them, and I got dinged on several judging sheets for them. Those beers fermented at the low end of the temperature range, according to the external probe, but they still ended up tasting hot. Combining that with the temperature difference I showed in the picture, I have a reason to believe the temperature measured with the external probe was inaccurate enough to cause issues.

As with everything, my experience is just that, my personal experience. I just wanted to throw out an example where the external probe mounting may not be ideal. I've learned that I get better control and better beers with a thermowell. For $14.00 (http://www.brewershardware.com/16-Stainless-Steel-Thermowell.html) and the price of a carboy hood, I know that my temperature is where I want it. It's definitely worth the price to me.

[BrewChemistinCO]

What step of fermentation is your yeast in? If you just pitch and you are going nuts then you should have a fair amount of circulation in the beer. I would bet that both the therm well and the outside glass temp are fairly similar.

If you have made it past the first few days or are conditioning then I would bet you see more variety. The thermal mass of the beer is pretty significant and the outside layers of your beer have probably dropped but your therm well is reading rig in the middle which would be the last to change.

The idea is similar to the jamil style wort chiller. Circulation causes quick heat transfer.